This disclosure relates generally to switching power converters, and in particular to communicating information received at a secondary side of a switching power converter to a primary side of the switching power converter.
Isolated switching power converters such as flyback and forward power converters may employ primary side sensing schemes to indirectly sense and regulate voltage output by the converter. The output voltage is sensed on a primary side of power converter at each switching cycle of the switching power converter. Such isolated switching power converters may employ pulse width modulation to regulate the output voltage under full, heavy load conditions. Under low- or no-load conditions, pulse frequency modulation may be used to regulate the output voltage, with the switching frequency being lowered as the load decreases.
As the switching frequency is lowered, it may become difficult for the isolated switching power converter employing primary side sensing of the output voltage to react to sudden changes in the load such as reconnecting an electronic device to the output of the switching power converter. Since load conditions are sensed at each switching pulse of the converter, the low switching frequency of the switching power converter under low- or no-load conditions may be too low for the converter to react to sudden changes in the load.
Furthermore, some isolated switching power converters are designed to work with a plurality of output voltages (e.g., 5V, 12V, etc.) as required by the electronic device connected to it. Such isolated switching power converters would receive a command signal from the connected electronic device indicating the output voltage required by the connected electronic device. The electronic device may also send other command signals relating to other requirements of the electronic device. Since the electronic device is connected to the switching power converter at the output of the power converter (that is, on a secondary side), such command signals are received on the secondary side of the switching power converter.